Replace Maestro GitHub PAT used in CI

[oleksandr-didyk]

Our scenario tests are currently relying on a personal GitHub PAT token for GitHub operations, such as clean-up.

We should replace it with a bot PAT token that is managed by secret manager.

[oleksandr-didyk]

Discusser over Teams and decided to add replace both GitHub PAT tokens used in the build pipeline:

• the scenario test one in the original scope of the issue
• the arcade-services read-write one used for creating releases

Additionally, decided to use the fine-grained token type to limit how much access each token gives

[oleksandr-didyk]

After the tokens are replaced, we need to clean-up:

• obsolete secrets from secret manager manifests
• obsolete secrets in Maestro and PCS Key Vaults
• obsolete variable groups and service connections used for the variable groups

Additionally, if we need to add any new variable groups or service connections we should make sure they have adequate ownership setup for the team

[oleksandr-didyk]

Removal of an obsolete reference to the previous Maestro scenario test token - https://dev.azure.com/dnceng/internal/_git/dotnet-release/pullrequest/44522

[oleksandr-didyk]

Removed obsolete variable groups from AzDO